Automatic telephone system



T.-G. MARTIN. AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FIILED DEC.8, 1917.

; UNITED STATES PATENT 'OFEICEZ TALBOT G. MARTIN, OF CHICAGO, ILLINOIS, ASSIGIQ'OR TO AUTOMATIC ELECTRIC- COMPANY', OF CHICAGO, ILLINOIS,'A CORPORATION OF ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM.

-Speciflcat1on of Letters Patent. Patented Dec. 14, 1920.

Application filed December a, 1917. Serial No. ,zoaaso.

To all whom it may concern:

Be it known that I, TALBOT G; Manrm, a citizen of the United States of Amerlca, and a resident of Chicago, county of Cook, State of Illinois, have invented certain new and useful Improvements in Automatic Telephone Systems, of which the following is a specification.

My inventlon relates in general to autoprovement on said prior application and in addition to the features shown therein, I have provided means, whereby when a subscriber of the branch exchange calls another subscriber in a distant office, an increased flow of current will be established through his line circuit to render his talking equipment more efiicient and to give a better quality to the speech over long lines.

The principal object of my invention is therefore to provide a simple and eflicient group of outgoing trunk lines extending to apparatus in connection with sub-exchange trunks which is made effective to increase the battery feed to the calling subscribers telephone when connection is'extended to a subscriber in a distant exchange and which apparatus operates only to complete a holding circuit for the individual switch of the calling station when a reverting call is set up.

Further objects and the manner of attaining them will be hereinafter more fully explained, reference being had to the accompanying drawing which shows a connection established from a subscriber in a branch exchange to a called line' in the main exchange in a system embodying the principles of my invention.

In systems of the above character the subscribers" lines terminating in a branch exchange may each be provided with ndividual line switches which have access to a the main exchange and terminating in selector switches thereat. When a'calling subscriber at a branch exchange lifts he receiver to initiate a call, his line is at once connected through to a selector switch at the mam exchange through the medium of his individual switch and an idle outgoin trunk line. Connector switches are provided at the sub-exchange for connecting with called lines therem and are accessible to selector switches in the main exchange over a second group of trunk lines.

Referring now to the figure of the drawmg, I have shown a sub-station A, which may be of the general type of substations shown in British patent to T. G. Martin No. 1419 of 1910. 'It consists of a transmitter 2, receiver 3, receiver hook 4, ringer 5, and

condenser 6. Being an automatic substation it is also provided with a pair of impulse springs 7 and 8 which are controlled through the medium of the usual finger hole dial and calling device mechanism '(not shown) to send out impulses over the line conductors 9 and 10 to operate the automatic switches. As the substation may be of the polystation type, a number of other similar stations may be bridged across the line conductors 9 and 10 in multiple with the substation A, each having a ringer similar tothe ringer 5 which will be tuned to respond to alternating currents of different frequencies.

The line conductors 9 and 10 terminate at the sub-exchange in the individual rotary 11118 switch C whichis of the general type of line switch shown in U. S. Letters Patent No. 1,186,471, granted June 6, 1916 to John A Erickson. Between the local and main exchanges are a number of trunk lines similar to that shown at D which lead from the banks of the individual line switches and terminate at the main exchange in selector switches of the well known Strowger type one of which I have shown at E. Each trunk line leading to the main exchange is provided :at the sub-exchange with a set ofrelays, one set of which'is shown at D and which comprises a slow relay 22 connected in series with the conductor 20 and shunted by a condenser, and an electropolarized relay 23 having one winding connected in series with the other trunk conductor 21 and also shunted by a condenser. The relay 24 is provided for maintaining a holding circuit for the line switch 0 and for closin the circuit of the polarizing winding 0% the relay 23. A relay 25 is also provided and is controlled by the relay 23 to cut the double scriber A removes his receiver he closes an' energizing circuit for the line relay 11 of the line switch G which extends from ground G, back contact of the lower springs of relay 12, line conductors 10 and 9 and substation A, back contact of the upper springs of relay 12, and through the relay 11 to battery. Relay 11, upon energizing over this circuit, attracts its armatures to ground the private normal from ground Gr and to prepare a circuit for the rotary magnet 13 at the upper springs. Assuming now that the wipers of the line switch (l are at this time resting in engagement with contacts leading to a busy trunk line, then as soon as line relay 11 attracts its armatures, current will flow from ground from some other occupying switch (not shown), over the private wiper 1G, springs 17 and 18, springs 19, and through the rotary magnet 13 to battery. The rotary magnet will therefore operate to advance the wipers 14:, 15 and 16 to terminals leading to another trunk line and will interrupt its own circuit in a well known manner. This operation of the rotary magnet will continue until an idle trunk line is reached, in which case there will be no ground applied to the wiper 16 and the circuit of the rotary magnet 13 will be opened. It will be observed that while the switch C was rotating the switching relay 12 was short-circuited through ground over wiper 16; as soon as this ground is removed therefore the said relay 12 will energize in series with the ro tary magnet 13 from ground Gr thereby disconnecting the line relay 11 and ground G from the line conductors 9 and 10 and switching said conductors through to the trunk line conductors 20 and 2] which lead to the main exchange. The relay 12, upon energizing, also switches its own holding circuit from the ground G at the springs of line relay 11 to the private wiper 16 which is supplied with ground from the trunk relays D as soon as the line is cut throu h in a manner to be explained.

As soon as the switching relay 12 cuts the talking conductors 9 and 10 through, an energizing circuit is closed for the line relay 50 of the selector switch E which is individual to said trunk line 20-21 at relay 50 to the trunk conductor 21, through the left hand winding of relay 23, and through the substation A and back over the trunk conductor 20 through the slow relay 22 and thence through u )per winding of said line relay to battery. The relay 22 will energize over this circuit and close a circuit for the slow acting relay 24: from ground, through spirings 34 and 35 and relay 24 to battery. elay 24 will now energize and attract its armature 43 to ground the release trunk to maintain the switching relay 12 of line switchC energized and will also close a circuit for the right hand polarizing winding of the relay 23. The relay 23 will not energize at this time due to the fact that current is flowing in, opposite directions through its two windings over the above traced circuits.

The calling subscriber may now operate his calling device for the first digit of the called number, thereby separating the springs 7 and 8 a predetermined number of times to open the circuit of the line relay 50 of the selector-E which operates in response to these interruptions to step the wipers 28, 29 and 30 up to some level in the bank in which are located contacts leading to connector switches which have access to the desired subscriber. Although the circuits of the two series relays 22 and 23 are opened each time animpulse is delivered over the trunk 20-21, this will have no effect upon the armatures of said relays; relay 22-being slow acting, will not allow its armature to fall back, while the right hand winding of relay 23 is not strong enough to attract the armature alone. As soon as the impulses of the first digit cease the selector E will rotate automatically in the usual manner to pick out an idle trunk line leading in this case to a connector H. lVhen the wipers 28 and 30 connect with the connector H a circuit is closed for the line relay 31, which extends from ground through the lower winding of said relay, wiper 30,

- and through the substation A over the circuit previously traced for the line relay 50 of selectorE and back through the wiper 28 and the upper winding of relay 31 to battery.

The calling subscriber then operates the connector H through the medium of his calling device in a manner well known in connection with switches of the Strowger type, to test and connect with the called substation. As soon as the called subscriber removes his receiver in response to the operation of his signal, a circuit will be closed for the back bridge relay 33 in the usual manner over a circuit including the two sides of the called subscribers line in series. The relay 33, upon energizing, attracts its ar- .matures to reverse the connections of the line relay 31 to the talking conductors,

\ thereby reversing'the flow of current over the trunk lines by means of which the connection has been extended, and through the calling substation.

The reversal of current causes the two windings of the relay 23 to assist each other and to therefore attract the armature 34 to close a circuit for the relay 25. The circuit for the relay 25 maybe traced from ground G through springs 36 and 37, springs 35 and 34, and through the relay 25 to battery. The relay 22 being slow acting, does not release its armature when this reversal of current takes place. The relay 25, upon energizing, bridges the doublewound coil 26 across the talking conductors 20 and 21 in parallel with the line relay 31 of the connector H, thereby increasing the current which flows over said trunk conductors and the calling subscribers line in series.

Let us assume now that the calling subscriber at A desires to call another subscriber on his own line, in which case, as pointed out in my said prior ajpplication, he will operate his line switch in the usual manner to select an idle trunk such as 2021 leading to a selector E in the manner before pointed out. The selector E will then be operated to select an idle ring back switch such as that shown at H and which maiy be connected to the contacts 38, 39 an 40 which are accessible to selector E. The ring back switch shown at H and the ringing equipment M are shown and described in my prior application.

After the subscriber has dialed the special number required'he'will then hang up his receiver, thereby causing the ring back switch to operate to ring both callin and called subscribers bells alternately. t will be noticed that when the calling subscriber hangs up his receiver and while the ringing is taking place, that the direct current circuit of relay 22 and also of the left hand winding of relay 23 are broken, while our- 1 rent from the ringing generators flows therethrough. Means has therefore been provided for maintaining the holding circuit for the switching relay 12 of line switch C closed to prevent the release ofthe connection.

A short time after the receiver is hung up at the calling su'bscribers station, the relay 22 of trunk relays D will deenergize and 0 en the circuit of the relay 24 and close a circuit at the springs 34 and 41 for the high resistance relay 27, which circuit extends over the lower talking conductor to battery through the low resistance relay 110 in the ring back switch. The relay 27 will immediately energize over this circuit to close another circuit through springs 36 and.

42 for the relay 24 and to also open a point in the circuit of the relay 25. It Wlll be seen therefore that the relay 24 will not have time to deenergize but willmaintain the circuit closed for the relay 12 of line switch C. Should the relay 23 vibrate with ringing current and operate to attract its armature 34 it will be seen that the circuit for the relay 25 will not be closed, due to the fact that the relay 27 maintains one point in said circuit open at the springs 36 and 37. As soon as the called subscriber answers, the circuit for the relay 22 will again be closed and conversation will take place in the usual manner and without the increased battery beggi g applied to the talking circuit.

hen the conversation is completed, the subscribers at both calling and called substations will replace their receivers, thereby opening the circuits of the line relay 100 of the ring back switch and causing the release of the rin back switch and of the selector switch in t e usual manner. In this case the relay 22 of trunk relays D will again fall back and open the circuit of the relay 24. The falling back of the relay 22 does not at this time cause the relay 27 to energize, due

to the fact that there 1s n0 batter on the trunk conductor 21 at the ring bac or first selector, which switches having both released. The relay 24 will therefore fallback after a short interval and open the circu1t of the switching relay 12 of the line switch C'and therefore cause the apparatus to be restored to normal.

It will be seen from the foregoing that lhave provided a simple and highly efiicient means whereby a polystation subscriber whose line terminates in a branch exchange, may call another subscriber in a distant exchange and whereby in such a connection an increased flow of battery will be supplied to his transmitter in order to increase the talking efliciency thereof. Also whereby such a means may be utilized to extend a connection to a ring back switch at the main exchange over a' two conductor trunk line for calling another subscriber on the same line and which will operate in a manner permitting said calling subscriber to, hang up his receiver to allow the called subscriber to be signaled and whereby the connection will not be released.

While I have illustrated and described one embodiment of my invention in connection with a specific type of apparatus it will be understood that I do not wish to limit myself to the exact form shown herein, but that my invention may be applied to various uses and types of apparatus. I desire therefore to include and have protected by Letters Patent all forms and modifications of my invention which may come within the scope of the appended claims.

What I claim as my invention is:

1. In a telephone system, a main ex- I change, a branch exchange, subscribers in each exchange, means whereby a subscriber .in the branch exchange may call another subscribers on a polystation line may call a subscriber on his own hne or one of the subscribers on one oi said other lines, means for supplying current for talking purposes to the calling subscribers line, means for increasing the supply of current to said line when a call is made to one of said other lines, and means for preventing the increase of current supply when the call is made to another subscriber on the same line.

3. In a telephone system, a party line, a trunk line, an automatic switch for connecting the two, a ring back switch, another line means for extending said connection to said ring back switch to signal another station on the same line, or for extending the connection to said other line, means for supplying talking battery current to said line in either case, a relay in said trunk line for maintaining said automatic switch in operated position independent of said party line when the connection is extended to said ring back switch, another relay for increasing the supply of talking current to said party line whenconnect-ion is extended to said other line.

4:. In a telephone system, a party line, a trunk line, an automatic switch for connecting the two, a ring back switch, another line, means for extending said connection to said ring back switch to signal another station on the same line, or for extending the connection to said other line, means for supplying talking battery current to said line in either case, a relay in said trunk line for maintaining said automatic switch in operated position independent of said partly line when the connection is extended to said ring back switch, another relay for increasing the supply of talking current to said party line when connection is extended to said other line, and means for preventing the opera- 1 ing the two, means whereby a subscriber on said party line may extend a call over said trunk line, either to another subscriber on said party line or to a subscriber on another line, means for supplying current for talking purposes to said line in either case, a relay in said trunk line for maintaining said automatic switch in operated position independent of said party line, another relay in said trunk line for increasing the talking current supply to said party line, and means for preventing the operation of said last relay when connection is extended to a subscriber on the same line. 1

6. In a telephone system, a party line, a trunk line, an automatic switch for connectin the two, means whereby a subscriber on said party line may extend a call over said trunk line, either to another subscriber on said party line or to a subscriber on another line, means for supplying current for talking purposes to said line in either case, a relay in series with said trunk line for maintaining said automatic switch in operated position independent of said party line, another relay in said trunk line for increasing the talking current supply to said party line,

and means for preventing the operation of said last relay when connection is extended to a subscriber on the same line.

7. In a telephone system, a party line, a trunk line, an automatic switch for connecting the two, means whereby a subscriber on said party line may extend a call over said trunk line, either to another subscriber on said party line or to a subscriber on another line, means for supplying current for talking purposes to said line in either case, a relay in series with said trunk line for maintaining said automatic switch in operated position independent of said party line, another relay in series with said trunk line for increasing the talking current supply to said party line. and means for preventing the. operation of said last relay when connection is extended to a subscriber on the same line.

8. In a telephone system, a party line, a trunk line, an automatic switch for connecting the two, a ring back switch, another line, means whereby a subscriber on said party line may either extend the connection to said ring back switch to thereby project ringing current back over said trunk line to signal another subscriber on the same line, or to said other line, means for supplying current for talking purposes to said party line, a relay in said trunk line adapted to increase the supply of talking current to said party line when the connection is extended to said other line, another relay in said trunk line, said last relay adapted to render "said first relay inoperative when connection is extended to said ring back switch.

9. In a telephone system, a party line, a trunk line, an automatic switch for connecting the two, a ring back switch, another line, means whereby a subscriber on said party line may either extend the connection to said ring back switch to thereby project ringing current back over said trunk line to signal another subscriber on the same line, or to said other line, means for supplying current for talking purposes to said party line, a

relay in said trunk line adapted to increase the supply of talking current to said party line when the connection is extended to said other line, another relay insaid trunk line, said last relay adapted to render said first relay inope'rative when connection is extended to said ring back switch, and means controlled by said first relay for maintaining said automatic switch operated independent of said party line.

10. In a telephone system, a party line, a trunk line, an automatic switch for connecting the two, a ring back switch, another line, means whereby a subscriber on said party line may either extend the connection to said ring back switch to thereby project ringing current back over said trunk line to signal another subscriber on the same line, or to said other line, means for supplying current for talking purposes to said party line, a relay in said trunk line adapted to increase the supply of talking current to said party line when the connection is extended to said other line, another relay in said trunk line, said' last relay adapted'to render said first relay inoperative when ringing current is projected back over said trunk line.

' 11. In a telephone system, a party line, a trunk line, an automatic switch for controlling'the two, a ring back switch, another line, means for extending the connection either to said ring back switch to signal a station on said party line or to said other line, means for supplying current for talking purposes to said party line, a relay in said trunk line energized thereover for maintaining said automatic switch in operated position independent of said party line, a polarized relay in said trunk line, means controlled by said polarized relay for increasing the supply of talking current to said party line, another relay controlled by said first relay for rendering said polarized relilay ineffective to increase the current sup- P y- 12. In a telephone system, a party line, a trunk line, an automaticswitch for connecting the two, a ring back switch, anothe; line, means for extending the connection either to said ring back switch to signal a station on said party line or to said other line, means for supplying current for talking purposes to said party line, a relay in said trunk line energized thereover for maintaining said automatic switch in operated position independent of said party line, a polarized relay in said trunk line, means controlled by said polarized relay for increasing the supply of talking current to said party line, another relay controlled by said first relay for rendering said polarized relay ineffective to increase the current supply, and circuits for each of said relays including a conductor of said trunk line.

13. In a telephone system, a party line, a trunk line, an automatic switch for connecting the two, a ring back switch, another line, means for extending the connection either to said ring back switch to signal a station on said party line or to said other line, means for supplying current for talking purposes to said party line, a relay in 'said trunk line energized thereover for maintaining said automatic switch in operated position independent of said party line, a polarized relay in said trunk line, means controlled by said polarized relay for increasing the supply oi": talking current to said party line, another relay controlled by said first relay for rendering said polarized relay ineffective to increase the current supply, a circuit for said first relay and said polarized relay including the two conductors of said trunk line in series, and the circuit of said last relay including only one conductor of said trunk line.

14. In a telephone system a main exchange, a branch exchange, subscribers in each exchange, means for extending a call from a subscriber in the branch exchange to either a subscriber in the main exchange or to another subscriber in the branch exchange, and' for supplying battery for talking purposes to the subscriber in the branch exchange, and means automatically operated only when the call is extended to the main exchange for increasing the talking current to the subscriber in the branch exchange.

15. In a telephone system, a party line, other lines, means for extending a call from a subscriber on the party line to another subscriber on his own line or to one of said other'lines and for establishing a flow of talking current in the calling line, and a relay operated automatically only when a call is to one of said other lines, for increasing said flow of talking current.

16. In a telephone system, a party line, means for extending a talking circuit from said party line and for establishing a flow of talking current in said talking circuit, means for reversing the flow of current in said talking circuit and a relay responsive to said reversal for increasing the flow of current in said talking circuit, and additional means for rendering said relay ineffective to increase the talking current when battery is reversed. l

Signed by me at Chicago, Cook county, Illinois, this 4th day of December, 1917.

TALBOT G. MARTIN. 

